Towers of Hanoi

hanoi.rb

@counter = 0
def move(n, source, target, spare)
    print('.') if @counter % 1000000 == 0 # let the user know that we are working for each 1,000,000th call
    if n > 0
        @counter += 1
        move(n - 1, source, spare, target) # move it to the spare so it is out of the way
        target << source.pop() # in place memory manipulation, equivilent to pass by refrence.
        move(n - 1, spare, target, source) # move the n - 1 disks that we left on spare onto target
    else
        return [source, target, spare]
    end
end

def tower(levels)
    start = *(1..levels)
    move(levels, start, [], [])
end

def simple_eta_genreator(levels)
    seconds = 2**levels - 1
    '%d days, %d hours, %d minutes, %d seconds' %
    # the .reverse lets us put the larger units first for readability
    [24,60,60].reverse.inject([seconds]) {|result, unitsize|
      result[0,0] = result.shift.divmod(unitsize)
      result
    }
end

moves = 25

puts("It would take you #{simple_eta_genreator(moves)} to do this. Give me some time...")
start = Time.now
res= tower(moves) #replace with height of tower
diff = Time.now - start
puts("\nMoves: #{@counter}\nResult#{res}")

Algo taken from Wikipedia: https://en.wikipedia.org/wiki/Tower_of_Hanoi#Recursive_implementation